Shredding or similar machines are subject to widely varying loading in operation and as a result of material blocking the cutting rollers are often decelerated to zero speed (stalled). Normally the drive motor is not switched off until this stage is reached. It is in part left to the operator to then switch off or reverse the motor, in order to remove the excess material blocking the cutting rollers. It is also known to increase power to the motor by connecting a second motor winding before the motor is stopped. This control is conventionally performed in current-dependent manner.